Polygonal realization under signed presentation isomorphism #
A signed presentation isomorphism may rename and independently reverse edge names, relabel faces, and cyclically rotate each stored face word. This file realizes those operations geometrically. The selected cyclic rotation acts on the circular polygon carrier by an exact complex rotation, so every labelled source side is sent to the target side carrying its relabelled dart.
The resulting homeomorphism of polygonal pre-realizations transports both the elementary gluing generators and their equivalence closures. It therefore descends to a homeomorphism of the faithful polygonal quotients.
The rotationUnit declaration.
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The rotateHomeomorph declaration.
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The rotateIndex declaration.
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Rotation sends a side to the correspondingly shifted side after changing only the phantom side-count index.
The target-boundary rotation selected for a signed presentation isomorphism.
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- e.faceRotation f = Classical.choose ⋯
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The target side occupied by a source side after the selected face rotation.
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The rotated target side carries exactly the relabeled source dart.
The disk homeomorphism on a face selected by the cyclic boundary rotation.
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A signed presentation isomorphism gives a facewise homeomorphism of polygonal pre-realizations.
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- e.preHomeomorph = IsHomeomorph.homeomorph (Sigma.map ⇑e.faceEquiv fun (f : P.Face) => ⇑(e.faceHomeomorph f)) ⋯
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On a labelled side, the pre-realization homeomorphism is exactly the selected cyclic shift.
Transport a boundary occurrence through the selected cyclic shift.
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The transported occurrence carries the signed relabeling of the source dart.
Transport of boundary occurrences is injective.
A compatible source pairing transports to a compatible target pairing.
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The pre-realization homeomorphism maps an occurrence-side point to its transported side.
Ignoring cyclic shifts, corresponding boundary-occurrence types have the same cardinality.
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- e.rawOccurrenceEquiv = e.faceEquiv.sigmaCongr fun (f : P.Face) => (Fin.castOrderIso ⋯).toEquiv
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The cyclic occurrence transport bundled as an equivalence.
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- e.occurrenceEquiv validQ = Equiv.ofBijective (e.mapOccurrence validQ) ⋯
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Pull a compatible target pairing back through the occurrence equivalence.
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Signed edge relabeling, face relabeling, and cyclic boundary rotation preserve the faithful polygonal realization.
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Propositional realization-invariance form used by elementary-move closures.